This verse is part of a larger argument posed to Jesus by the Sadducees. The Sadducees didn't believe in the resurrection, and they were trying to trap Jesus in a logical contradiction, thereby discrediting the idea of resurrection. Here's a breakdown:

The Scenario: The Sadducees present a hypothetical scenario based on the Jewish law of levirate marriage (Deuteronomy 25:5-10). If a man died without having children, his brother was obligated to marry the widow and raise up offspring for the deceased brother's line.
The Setup: They describe a woman who successively marries seven brothers, each dying without producing offspring.
The Question: They pose the question, "In the resurrection, whose wife will she be of the seven? For they all had her." This question is designed to make the concept of resurrection seem absurd. They assume that marriage in the resurrected life would be the same as marriage in earthly life, with the same rules and expectations.
The Underlying Intent:
To Deny the Resurrection: The Sadducees are fundamentally trying to ridicule the belief in resurrection. They believe that if the idea of resurrection leads to such logical absurdities, then resurrection itself must be false.
To Embarrass Jesus: They hope to publicly embarrass Jesus by making Him appear foolish or unable to answer the question.

In essence, the Sadducees are presenting a scenario they believe makes the resurrection seem ridiculous and untenable, based on their understanding of earthly marriage. They are trying to trap Jesus into saying something that could be seen as illogical or that would undermine His authority.